1. Field of the Invention
The present invention generally relates to a single wavelength bi-directional optical transceiver including a transmitter and a receiver which have the same wavelength, and, more particularly, to a two-way single wavelength optical transceiver with a structure for avoidance or cut-off of an optical path to prevent optical signals from a transmitter from being introduced into a receiver in order to overcome a problem that the receiver detects and recognizes a signal output from the transmitter, rather than a forward signal (a signal transmitted from a counterpart optical transceiver), as a forward signal, that is, an optical crosstalk effect.
2. Description of the Related Art
In recent years, with increasing use of wired/wireless communication, faster transmission of more data has required higher capacity, lower loss and higher speed communication systems. Optical communication systems meeting these conditions have been a focus of attention.
Optical communication can be classified into a full duplex type and a bi-directional type in terms of the transmission approach employed. The bi-directional transmission type may also be subdivided into a single wavelength transmission technique and a two-wavelength transmission technique.
In use of the single wavelength transmission technique, it is necessary to employ the same optical transceiver at both ends of a communication system. Single wavelength bi-directional transmission means that data can be bi-directionally transmitted at a single wavelength on the same transmission line at once.
FIG. 1 is a view of a general single wavelength bi-directional transmission approach. As shown in FIG. 1, two single wavelength bi-directional optical transceivers are employed for the single wavelength bi-directional transmission approach. A single wavelength bi-directional optical transceiver includes a transmitter and a receiver which are integrated into a single body. In addition, use of single wavelength requires a 50:50 optical filter (or a 3 dB optical splitter) to separate one signal from another, instead of a wavelength division multiplexing filter. The single wavelength bi-directional transmission approach is more economical than other transmission approaches in terms of installation and maintenance costs because it is able to transmit data through the same optical fiber. In addition, this approach has another advantage of easy installation as a supplier and a recipient use the same wavelength and the same optical transceiver.
The single wavelength bi-directional optical transceiver is able to transmit/receive signals with the same wavelength, which requires a filter or an optical splitter having a 50%-transmission and 50%-reflection capability. As described above, when a transmitter is driven, 50% of an optical signal is transmitted while the remaining 50% is reflected. In this case, only the transmitted 50% of the optical signal acts to be coupled to an optical fiber, whereas some of the remaining reflected 50% of the optical signal is reflected and incident into a receiver. This is called an “optical crosstalk” effect wherein a forward signal is affected by such incidence of some of a signal from the transmitter into the receiver. This optical crosstalk is an important issue in a single wavelength bi-directional optical sub-assembly (BOSA) structure.
Although the single wavelength bi-directional optical transceiver is useful due to its easy installation and low maintenance costs as described above, the optical crosstalk may result in communication services with poor signal sensitivity in real world situations.